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Introduction

SPC was originally written to process data written by SPECTRA, the spectral-line observing program of the Parkes radiotelescope. While SPC's data structure and many of its commands are Parkes-specific it has been adapted for use by a variety of other telescopes (e.g. the AT, Nobeyama). The latest version recognizes a number of data formats; the the original .SPC files still written by SPECTRA, RPFITS format data files written by the AT correlator, Single-dish FITS (SDFITS) files written by various utilities, including SPC itself, and the old memory-dump format produced by SPC(the .SAV files which may no longer be written).

The basic idea in using SPC is to load in a sequence of up to 110 spectra and then use various commands to operate on these spectra. The locations available in memory for holding spectra are referred to as registers. Some operations involve using a reference spectrum, for example, forming quotient spectra from a series of signal spectra and a reference. Register 111 is conventionally reserved for the reference spectrum. Reduced spectra may be written to a disk file (WRITE) for storage in single-dish FITS format. These SDF files can be read again into SPC for further processing. SPC registers may be appended to an existing SDF file thereby providing a convenient way of organizing spectral data.

SPC commands are minimum-match; i.e. the shortest unambiguous abbreviation (usually two letters) may be used. A brief list of the most often-used commands occur with the command prompt; the complete list is given in this document. Since the interactive format is question and answer, which can be a lengthy process, a shorter form of the command (ending in a period) may be used. This skips many of the questions, using the previous answer as the default. Previous answers are (almost) always kept as defaults for both full and short forms of a command.

Brief history:

Origins
Rick Forster, project scientist for the construction of the Australia Telescope, designed and wrote the first version of SPC, then called S. He also wrote the first version of this manual.

Porting
SPC was developed on a VAX and made liberal use of the VMS extensions to FORTRAN. When the ATNF migrated from a predominantly VMS-based computer system to predominantly unix-based the port of SPC was done by Henrietta May who also maintained it for many years after Rick Forster left the ATNF. The name change from S to SPC was required by the unix port.

Expansion
In early 1992 a new Parkes correlator was installed which produced data with a larger number of channels. The channel limit in SPC was increased from 1024 to 4096 by Azimul Hoque.

PGPLOT
The original version of SPC used in-house plotting packages (MIXPLOT and AUTOPLOT) and these were translated to the widely-used PGPLOT plotting package by Simone Magri.

Extension
Mark Calabretta became the SPC maintainer in 1997 and made further developments aimed at making it more generally applicable:

• Added Single-dish FITS reading and writing capability.

• Added RPFITS reading capability, including accumulation of spectra on input.

• Added support for Parkes multibeam data.

• Ported to the Linux operating system (with assistance from Chris Phillips).

• Corrected and updated this manual and converted it to L^ATEX.

The SPC distribution kit is available from the ATNF (Australia Telescope National Facility) web page, .

This document is composed of four parts:

Part I This introduction.

Part II General information for using SPC. How to load data, saving and reporting results, description of the working registers, etc. Also contains a section on how to make changes in SPC.

Part III A list of the commands available in SPC, listed by type and function, and also alphabetically. A brief description of the inputs and outputs and the command algorithm is given in the tables, and a complete description of the commands follows.

Part IV A description of the header information available. These items control things like the velocity axis for plotting, source name, etc. Header items can be edited if required.